What are the factors that determine the quality of walnut?

Referring to UNECE, the quality factors of walnuts are based on oil content, size, color, and nut defects. The walnuts are sorted throughout processing into three classes (extra, I, II). This is decided by size and color (extra light to amber). Examples of defects that are looked for and sorted out during processing are mold/rot, shell fragments, and insect damage. Defects that are allowed some tolerance are dark kernels, mold/rot, and scuffs.

The purpose of the standard is to define the quality requirements for walnut kernels at the export control stage, after preparation and packaging, further as follows:

Walnut Minimum Requirements (referring to UNECE)

a) In all classes, subject to the special provisions for each class and the tolerances allowed, walnut kernels must be:

• Sufficiently dry to ensure keeping quality;
• Sound; produce affected by rotting or deterioration such as to make it unfit for consumption is excluded;
• Firm;
• Sufficiently developed; shriveled kernels are to be excluded;
• Clean, practically free from any visible foreign matter and from shell;
• Free from insects or mites whatever their stage of development;
• Free from damage caused by pests ;
• Free of any rancidity or oily appearance;
• Free from mold;
• Free of abnormal external moisture; and
• Free of foreign smell and/or taste.

The condition of the walnut kernels must be such as to enable them:

- To withstand transport and handling; and

- To arrive in satisfactory condition at the place of destination.

b) Moisture content

The walnut kernels shall have a moisture content of not greater than 5 percent.

Walnut UECE Classification

a) "Extra" Class

Walnut kernels in this class must be of superior quality, uniformly light-colored with practically no dark straw and/or lemon-yellow color and with no dark brown. They must be characteristic of the variety and/or commercial type. They must be practically free from defects with the exception of very slight superficial defects provided that these do not affect the general appearance of the produce, the quality, the keeping quality, or its presentation in the package.

Scuffing is allowed on:

- Quarters and all pieces; and

- Halves, provided it covers no more than 10% of the surface area of the skin.

b) Class I

Walnut kernels in this class must be of good quality, of color not darker than light brown and/or lemon-yellow. They must be characteristic of the variety and/or commercial type. Slight defects may be allowed provided that these do not affect the general appearance of the produce, the quality, the keeping quality, or its presentation in the package.

Scuffing is allowed on:

- Quarters and all pieces; and

- Halves, provided it covers no more than 20% of the surface area of the skin.

c) Class II

This class includes kernels that do not qualify for inclusion in the higher classes but satisfy the minimum requirements specified above. Walnut kernels in this class must be of color not darker than dark brown. Darker kernels may be marketed in this class, provided the color is indicated on the package. Defects may be allowed, provided that the walnut kernels retain their essential characteristics as regards general appearance, quality, keeping quality, and presentation. This class also includes mixtures of kernels of different colors and is designated in the marking by the words 'mixed colors'.

Scuffing is not considered a defect.

Source: UNECE STANDARD DDP-02 concerning the marketing and commercial quality control of WALNUT KERNELS